Rhodium(III)-Catalyzed C–H Activation: A Cascade Approach for the Regioselective Synthesis of Fused Heterocyclic Lactone Scaffolds

A Rh­(III)-catalyzed cascade C–H
activation; regioselective
[4 + 2] oxidative annulation; and lactonization of aromatic acids,
anhydrides, and acrylic acid derivatives with 4-hydroxy-2-alkynoates
have been disclosed. This strategy leads to fused heterocyclic lactone
scaffolds in a single step with moderate functional group tolerance
and excellent site selectivity. Besides, in one step, an antipode
of the cephalosol intermediate natural product that contains a tricyclic
isocoumarin framework has been synthesized.